Boxing and overall strengthening...
Boxing and overall strengthening of the lower-control-arm mounting points is critical. This will not only prevent damage to the car, but will help it transmit power more efficiently.
Serious racers may want to...
Serious racers may want to consider some weight-saving chassis components, such as a coilover strut kit (top), which also enables you to effectively adjust the nose height, tubular A-arms (middle), and a tubular K-member (bottom), like these pieces from Ground Pounder Products. The less weight on the front of the car, the easier it is for the nose to lift and transfer weight to the rear tires. For the same reason, lightweight wheels and tires are a good idea.
There is a variety of subframe...
There is a variety of subframe connectors on the market, and all of them are better than having none at all. Most are bolt-in designs, but both Hilliard and Hupp recommend having them welded in place.
The rotation of the engine...
The rotation of the engine and drivetrain affects traction because it twists the chassis and loads each tire differently. This is why the Eibach Pro Launch springs have different rates at each corner--to compensate for this weight transfer and launch the car straight.
Using the right springs and...
Using the right springs and struts/shocks will make a world of difference in how your car hooks. Eibach makes drag-specific springs, while Lakewood, AVO, and Koni all offer struts and shocks designed for drag racing.
The stock control arm (top)...
The stock control arm (top) is fitted with large, soft rubber bushings. While certainly more comfortable on the street, rubber bushings don&8217t do a very good job of transmitting load to the chassis. Whether you plan to drag race or road race, the lower control should be replaced with an aftermarket control arm (below) fitted with harder urethane bushings. For serious drag racing, aluminum bushings should be considered.
Pinion angle plays a big part...
Pinion angle plays a big part in how hard the car launches. With a sturdy rear suspension (such as with boxed control arms and hard bushings), the rearend doesn’t rotate much, so pinion angle doesn&8217t change a lot. Typically, the more the pinion points down (negative pinion angle), the softer the hit to the tires.
You can&8217t adjust pinion...
You can’t adjust pinion angle with stock control arms, but HP Motorsport’s Mega-Bite upper arms allow for some adjustment. They also allow you to straighten the rearend in the car if it&8217s not already.
Make sure the rearend is pointing...
Make sure the rearend is pointing dead ahead in the chassis. If it&8217s not, the car will never go straight. Bent control arms or misadjusted adjustable arms will cock the rearend.
This is something to remember...
This is something to remember before you get your Mustang launching like a Pro Stocker: a driveshaft loop. The NHRA mandates it, and it’s a good idea in any car regardless of power. You don’t want the driveshaft or U-joint breaking and digging into the track. It tends to pole-vault the rear of the car, and that&8217s not good.
Drag shocks/struts are often...
Drag shocks/struts are often called "90/10s," which means 90 percent of their resistance is in compression (bump) and 10 percent is in extension (rebound). This allows the shock to extend rapidly and not restrict the nose of the car from lifting, then slowly settle back down to ride height after the car is launched. The really good, expensive shocks/struts, such as the Konis, are adjustable.
Making power with a 5.0 is easy. Putting that power to the ground is another matter entirely. Almost all street/strip 5.0s have the same chassis mods: subframe connectors and a traction device of some sort. That's about it.
The main reason is that most of us simply don't understand chassis dynamics, or what happens to our car the instant we put our foot to the go-pedal. And unlike an engine kit, you can't simply call up a mail-order warehouse and ask for the "Super Hook Package" guaranteed to produce neck-snapping 60-foot times. Most of the time, it's trial and error; you may go through several different traction devices, tire sizes, gear ratios, and other expensive equipment before you find a way to make your car leave properly.
To put it mildly, this sucks. There's nothing worse than spending your "discretionary income" on parts that you end up selling later because they didn't work the way you'd hoped. So we decided to do something about it. We talked to a couple of guys who know a little bit about Mustang chassis and going fast. On the hard-core side of the fence, we talked to Charlie Hupp of Charlie Hupp Race Cars in San Dimas, California, who has been building race-car chassis for over 17 years (four of which were spent at world-famous Brogie Race Cars as shop foreman) and has several NHRA records and four NHRA "Best Engineered" awards to his credit.
On the flip side, we talked to Dennis Hilliard at Central Coast Mustang in Santa Maria, California. In business since 1979, Dennis is one of the veterans of the Mustang performance-parts business, and he takes great pride in building both cars and engines that really work, without trick parts or a huge cash outlay.
To put this story in some semblance of order, we're going to start with the front of the car and work our way back. If you listen to what these two gentlemen have to say, we can almost guarantee your car will leave harder and go quicker than it does right now.
On the Nose
The one thing our men touched on immediately was the front struts. If you're serious about drag racing, throw away the stockers and replace them with 90/10 drag struts. If your car is a dual-purpose street/strip piece, then consider 70/30 struts to maintain a street-worthy ride. "If money isn't a problem, Koni's adjustable drag struts are the best," comments Hilliard. In addition, he recommends removing the front sway bar, as he maintains it will "loosen up the front end" and help the car react and 60-foot better. Hupp, on the other hand, doesn't see much of an advantage to removing the front sway bar and says it will also sacrifice the car's handling around town. When in doubt, try the car at the track both ways and see what you think works best.
When it comes to springs, long, low-rate springs are recommended to give the car maximum rebound. "On a street/strip car, you want the front end sitting a little bit high," says Hupp, "because this starts the weight transfer a little quicker. It doesn't look cool, but you'll notice that the fast guys have their car set up maybe an inch or two above level."
As you might have guessed, alignment and your choice of front rubber are also very important once the car is moving. Hilliard has specific recommendations in this department: "I always align the front end with the weight of the driver in the seat. Also, considering that the car will not run at static ride height down the track, I will put in about 1/2- to 3/4-inch degrees of negative camber and about an 1/8-inch toe out at static ride height. This will maximize the car's performance as it heads down the track with the nose up."
With a wheel-and-tire combo, the idea is to reduce weight as well as rolling resistance. On serious street/strip or drag-only cars, a lightweight 15x3- or 15x3.5-inch front rim should be used, along with the appropriate skinny front rubber to keep rolling resistance down to a minimum.
The faster you go, the more chassis modifications your car will require, not only to make it work better, but to save your ass in the event of a wreck. Always contact your sanctioning body to find out what type of rollbar/cage and other chassis modifications are necessary in order to make your car safe and legal for competition at your particular e.t. level. What we're going to talk about here is simply the stuff that will make the chassis work.
Subframe connectors are the single most important chassis modification you can make to your Mustang. If you've already got them in place, you're one step ahead of the game; if you don't, all you have to do is drive a car with them and you'll see why they're needed. In any case, both Hilliard and Hupp recommend you weld them in place, even if they're bolt-in units. Hupp also recommends that you don't stop at the ends of the connectors, but rather you continue to weld the connectors to the rocker panel, about a 1-inch weld every 4 inches, being careful not to burn through the sheetmetal floor. "Any type of gusseting you can do along the way will help as well," he says. Depending on how fast your car is, it may need a rollcage to satisfy rules requirements; a cage does wonders to stiffen the chassis.
The upper- and lower-control-arm mounting points (or boxes) are also an area of concern, as they bear the brunt of the load as the car accelerates. Hilliard recommends that you weld over the seams wherever possible, while Hupp has a more specific recommendation: "On your lower-control-arm boxes, weld a piece of 1/8-inch sheetmetal to the mounting hole. Just drill a hole in it, and weld it in place. From the factory, these [torque boxes] are only 1/16-inch thick. All of the weight of the car goes through these mounting points when the car launches. On a 1.5g launch, which is typical, we're talking about 4,500 pounds of force going through those sheetmetal bolt holes."
The Business End
A lot of things happen at the rear of your car when you leave the starting line, so it's important that you spend some quality time here. You also have to decide where you will be doing the bulk of your driving (street or track), because many drag-oriented suspension mods can give your Mustang a harsh, noisy ride on the street. If you want the best of both worlds, we think Hilliard's recommendations are tops: "I'd start off with Eibach Pro-Launch springs," he says. "They come in two different rates for the right and left side of the car, and I'd recommend running an air bag in the right rear as well. For shocks, I'd use Lakewood 50/50 or Competition Engineering adjustable units. Lakewood traction bars are my pick, as they're not as hard on the body as some of the other types that replace the lower arms. Those have solid bushings that beat up the car pretty bad." Sounds simple enough.
Now, remember when we said Hupp was hard-core? Get ready for Rear Suspension 101. "From the factory, the Mustang rear suspension is similar to a four-link," Hupp notes. "If you replace the bushings with solid aluminum pieces, it will function exactly like a four-link. You can box the stock control arms and fit them with aluminum bushings, and that will work. But if you really want to optimize [the rear suspension], you need to re-set your pinion angle, which can be done with a slightly longer-than-stock lower control arm. Factory is about 0-2 degrees down; you want 4-6 degrees. For really bad street/strip cars, I would recommend using aluminum bushings on the lower control arms and hard urethane bushings on the uppers to provide some sort of happy medium." All of this, Hupp amends, is provided you strengthen and reinforce the torque boxes first.
"For shocks, I like something in the range of 60/40 to 70/30, depending on how much traction you need," Hupp continues. "A 60/40 typically won't hook as well as a 70/30, but you don't want the shocks to be any softer than necessary. If you have a three-position shock, start off with the 50/50 setting. If it works, leave it alone. If not, go to the next-softer setting."
Whatever shocks you have, Hupp says it's crucial that they sit on the car a little more than halfway compressed. "Take the shock off the car, compress it completely, then mark it. Extend it completely, then mark it again. Put it back on the car, and see where it sits." And if it isn't better than halfway compressed? "Remove the rear springs and cut an inch off the coil at a time (linear length, not height) until the shocks sit properly. This will ensure the shock has enough travel to allow the rear end to come down and plant the tires."
Tires and Gears
Our two gurus agree that anything more than a 10-inch tire on a 10-inch rim should not be necessary (all the way down into the 9-second zone), but what diameter you choose depends on your power level and gear ratio. Hilliard is used to making prodigious amounts of power with his blown 5.0s, so he typically relies on a 28-inch-tall tire and a gear ratio anywhere between 3.55 and 4.11, depending on the particular application.
If you're not sure what to use on your car, Hupp recommends you try a smaller 26-inch-diameter tire and work your way up. And gears? He maintains there simply is no hard-and-fast rule for any car.
"The rearend gear is really important. You want to go through the lights as close to maximum shift rpm as possible. If you're a psycho full-race guy, you really want to be about 500 rpm over--that's what goes fast.
As you can see, there are more than a few ways to arrive at the same goal: making your 5.0 hook. Obviously, your level of commitment and the fatness of your wallet will dictate which methods you choose. But if you follow the advice of the experts, you can get there from here--and very quickly.